1. Field of the Invention
The present invention relates to a bag forming unit and is particularly related to an apparatus for making plastic bags from plastic sheet materials such as, for example, polyethylene, polyester, and the like. More specifically, this invention contemplates providing a bag forming unit which is an attractive, portable household appliance and which can be readily and conveniently used by the housewife for making plastic bags of predetermined sizes for wrapping sandwiches and for preserving various foods in order to prevent them from premature drying and from contamination or decay until future consumption.
Still more specifically, the present invention relates to a bag-forming apparatus which includes several unique features designed to eliminate some of the difficulties which have been encountered in the prior art bag-making apparatus.
2. The Prior Art
A variety of plastic bag fabricating units are currently available in the market place and some of these units have found their way into various homes as household appliances. Several such units are described in U.S. Pat. No. 3,354,017 which issued to W. H. Laeger et al on Nov. 21, 1967; U.S. Pat. No. 3,753,829 which issued to Max Freeman on Aug. 21, 1973 and U.S. Pat. No. 3,847,712 which was granted to Robert G. Hubbard on Nov. 12, 1974. As described in Freeman, the early methods of sealing of the adjacent edges of separate plastic sheets were accomplished by "impulse sealing" which involves the simultaneous application of heat and pressure to the plastic sheet materials to form the bags. Impulse sealing, however, requires complicated equipment for closely controlling the exposure time and temperature.
In his aforementioned patent, Freeman describes a plastic bag fabricating, dispensing and sealing unit which utilizes a heated wire for simultaneous sealing and severing the dispensed bags. This unit includes a compartment which houses a cartridge containing a roll of double-layered plastic film formed by folding and winding a single layered sheet along its longitudinal axis. Bags are thus formed having three closed edges and an open edge for receiving the consumer items.
The bag making apparatus described in the aforementioned patent of Laeger et al is basically designed to form plastic bags by dispensing the film from a compartment in the unit and sealing and severing it much in the same manner as the apparatus described by Freeman.
While some of the prior art bag forming units include both means for sealing and for severing the plastic bags from the plastic roll of film, others, such as the apparatus described in the aforementioned Hubbard patent are only equipped with a sealing means. In this type of apparatus, the roll of plastic film, which is sealed along three edges, is dispensed from a compartment within the unit, sealed along its leading open edge and then torn along this edge to sever the bag from the roll of plastic film.
For one reason or another, none of the prior art units have found widespread acceptabiity either due to inconvenience in their use, inherent poor performance characteristics or basic lack of safety features. For example, the apparatus described in the aforementioned Hubbard patent does not include means for severing the bags from the roll of plastic film and the bags are torn manually. On the other hand, the Freeman unit provides a heated wire which is exposed and therefore could cause serious accidental burns to the housewife or children in the household. The aforementioned and other disadvantages of the prior art bag forming units will become more apparent from the ensuing description of the apparatus of this invention.